The invention relates to a toothed rotor set for a pump or an engine consisting of a rotating outer rotor. There is an inner rotor inside the outer rotor, which has bearing (oil) pockets for planetary gears. The toothed rotor set is similar to a ring pump with toothed execution. The function and procedure of the toothed rotor set correspond to the function and procedure of a toothed ring pump.
In toothed ring pumps, the pressure chamber is not separated from the suction chamber by a sickle shaped filling piece. Instead, a special shaping of the teethxe2x80x94based on the trochoidal teeth systemxe2x80x94ensures the sealing between the toothed ring and the outer toothed-pinion. The ring with inner teeth has one tooth more than the pinion, so that if the teeth are shaped properly, the tooth crests touch the exact tooth contact point. To ensure rolling, there must be a crest clearance between the tooth crest of the outer rotor and the tooth crest of the inner rotor. The disadvantage in the case of the ringed pump is that this crest clearance causes inner leakages that in turn lead to bad volumetric performance. In fact, at low speeds, it is not possible to build high pressures for this reason.
In comparison to a ringed pump, it is more advantageous to have a pump conforming to the principle of DE A 196 46 359. The pump is designed as a toothed rotor set consisting of a bearing ring with an inner tooth system and a gear placed eccentrically inside it, having outer teeth. The inner tooth system is formed by rollers that can rotate in the bearing ring, and it has one tooth more than the outer tooth system. A fine teeth system with an essentially smaller module is superimposed on the outer teeth of the gear.
Each roller has a fine tooth system on its circumference with the same module with which the teeth of the gear interlock.
The function of the toothed rotor set is that a drive momentum impacts against the inner rotor through a drive shaft, and makes it rotate. The toothed inner rotor transfers a force to the planetary gear, which on one hand manifests itself as an impact through the center of the planetary gear, and on the other, as a radial force that creates a torque for the planetary gear. The impact on the bearing ring causes it to rotate.
The known toothed rotor set has the disadvantage that a large number of planetary gears must be used to enable the function. And the use of a large number of planetary gears results in relatively higher incidence of friction, which the torque of the drive shaft connected to the inner teeth system must overcome. Another disadvantage of known toothed rotor sets is that when the inner rotor rotates, lubrication oil (grease) rotating in the same direction flows into the gaps between the teeth of the planetary gear from the pressure side to the suction side, and this flow lowers the efficiency of the pump.
The disadvantages of the latest technology status highlight the task of creating a toothed rotor set designed in such a way that for the same model size, a lesser number of planetary gears is used to reduce the incidence of friction. The task of the invention is also to create a toothed rotor set that offers larger pumping volumes and higher efficiency at comparable model sizes, than the known toothed rotor sets.
The problem is solved according the invention, by a toothed rotor set for a pump or an engine consisting of a rotating outer rotor with an approximately star shaped bore. The bore has a fine inner teeth system and an inner rotor aligned eccentrically inside it, having oil pockets for planetary gears.
The planetary gears have a fine teeth system with which they roll in the fine teeth system of the outer rotor. The outer teeth system has one tooth less than the inner teeth system of the outer rotor. The advantage of a toothed rotor system designed in this manner is that in comparison to known toothed rotor sets from the latest status of technology, the toothed rotor set conforming to the invention can be driven by a smaller number of planetary gears. This is because for the same model size, a smaller number of planetary gears are used than in the known toothed rotor sets conforming to the latest technology status. Smaller number of planetary gears further means smaller friction areas for example, between the planetary gears and the oil pockets of the inner rotor as well as between the teeth of the planetary gear and the teeth of the outer rotor. Less friction means that a pump or engine with a toothed rotor set conforming to the invention has greater efficiency than the pump or engine with the known toothed rotor set conforming to the latest technology status, because lesser torque must be used to overcome the friction in the system. From the perspective of design, the toothed rotor set enables a higher pumping volume than the known toothed rotor set conforming to the latest technology status.
In addition, the toothed rotor set conforming to the invention has a higher efficiency because when the inner rotor rotates in the clockwise direction, the planetary gears rotate in the anti-clockwise direction leading to an additional flow of lubricating oil in the gaps between the teeth of the planetary gears from the suction side to the pressure side.
A further problem of the fine teeth system is that the forces and moments that come into play are not optimally accepted by the involute teeth systems used thus far in the toothed rotor sets conforming to the traditional genre. In particular, there is the problem that the known teeth systems do not transfer the impact and radial forces in the linear direction without a high degree of surface friction.
The thus far known teeth systems are suitable only for transferring large radial forces and not for transferring large impact forces that travel through the center of the planetary gears.
A disadvantage of the genus-building toothed rotor set is that it does not ensure clean rolling under all operational conditions, without interlocking disturbances. The movement of the planetary gears relative to the bearing ring eventually comes to a standstill.
In this condition, when the planetary gear is almost stationary and simultaneously, a large force is transferred, there is the real danger that the lubrication film between the tooth crest of the planetary gear and the bearing ring may burst, leading to stoppage of the oil flow. The result is fixed body contact through the loss of lubrication oil in the crevices. Favorable hydrodynamic lubrication conditions are no longer there, and these have been replaced by conditions of hybrid friction, which, in the worst scenario case can end in jamming. In case of mixed friction or jamming, erosion takes place, thus reducing the life of the toothed rotor set.
In an advantageous design of the toothed rotor set conforming to the invention therefore, at least one section of the inner and/or outer fine teeth has an arched component. The advantage of a toothed rotor set designed in this manner is that due to the arched component, rolling friction takes place, but no sliding friction is possible, so that erosion of the teeth is minimized.
The convex shaped tooth crest of the fine-toothed planetary gear and the concave shaped tips of the fine-toothed outer rotor ensure that there is surface contact but no linear contact. The Hertz pressing is reduced considerably through this roller pair.
By incorporating a flank clearance between the teeth of the planetary gear and the gaps in the teeth of the outer rotor, it is ensured that transmission of the larger impact forces takes place only over the tooth crest and the tooth tips. This way it is ensured that no large wedging forces impact on the flanks of the tooth system. Such impacts can destroy the flank surfaces. Additionally, the lubrication oil from the gaps between the teeth can flow out through the flank clearance, as otherwise, it might lead to squeezed oil, which can lead to the formation of high pressure.
In an advantageous design of the toothed rotor set conforming to the invention, the crest and/or the tip areas of the teeth are designed in the form of an arc. This kind of shaping of the teeth in the region of the crest and/or tip enables very large impacts (radial forces) to be transmitted. In this process, the part of the radial force to be transferred can be small. In this case, the tooth crest and tip is included in the rolling process, i.e., rolling of the toothed planetary gears on the toothed outer rotor curve, unlike in the case of toothed rotors of known involute teeth systems.
The convex curved tooth flank of the planetary gear and the concave curved tooth flank of the outer rotor create a relatively large contact area during interlocking, which seals the compression chamber during the movement of the compression chamber from the suction area to the compression area. Even deviations in the rectangular alignment of the rotor do not lead to leakage losses in the compression chamber.
In an advantageous design of the invention, there is the provision that particularly the region of the tooth crest and/or tip of the fine tooth system has a flattening. In the main region of force transmission, in which the torque of the inner rotor operates on the toothed outer rotor through the toothed planetary gears, the planetary gears almost come to a standstill. Under conditions of the described relative stationary status, and the simultaneous transmission of a large force, there is the danger that the lubrication film between the planetary gear tooth crest and the oil pockets of the inner rotor may burst.
The tooth crests of the planetary gears were flattened to prevent this. The size of the flattening depends on the use area of the toothed rotor. At low speeds and high pressures, a strong flattening is necessary to ensure the formation of a lubrication film even at low sliding speeds. At high speeds and low pressures, a small flattening is required. A special curvexe2x80x94the cycloid curvexe2x80x94is used for the transfer from the tooth crests of the planetary gear to the flattened surface, which supports the formation of a lubrication film better than a simple transfer radius.
In a further advantageous design of the invention, especially the region of the tooth crest and/or tip has a large curvature radius. Instead of a flattening, it is meaningful to provide a surface with a large curvature radius in the region of the tooth crest and/or tip.
The flattening of the tooth crests of the planetary gear leads to an improvement in force transmission (Hertz pressing) from the planetary gear to the inner rotor.
In a particularly advantageous design of the invention, the arc shaped component is at least partially designed as a cycloid. The cycloid has proved to be especially advantageous in relation to the rolling process and the transmission of impact forces. This cycloid teeth system ensures that even for wide curvature changes and small curvature radiuses, the rolling is smooth and almost slide-proof, leading once again to reduced wear and tear.
In a purposeful design of the invention, the teeth are shaped as involute teeth, at least in the region of the tooth flanks. In this kind of teeth system, the tooth flanks of the toothed outer rotor and the toothed planetary gears are formed through an evolutionary process, so that in this execution model, the interlocking disturbances can be less than in the case of the execution model in which the tooth flanks are designed as cycloids.
In an advantageous design of the invention, the fine teeth system is provided with a near erosion-proof surface. The erosion-proof surface can be achieved easily through a chemical, especially thermo chemical or physical treatment. In addition, the surface can be galvanized. Further advantageous surface treatment processes include carborizing, nitriding and/or nitro carborizing, coating with boron and/or chromium.
In an advantageous design of the invention, at least one fluid duct is provided in the oil pocket region. The fluid duct can be connected to the pressure side of the pump so that there is a constant flow of lubrication oil between the planetary gear and the oil pockets. This ensures an improved formation of lubrication film.
All moveable components of the toothed rotor set, especially the outer rotor and/or the planetary gears and/or the inner rotor have the front side of at least one rotating crosspiece. This rotating crosspiece serves as sealing for the casing in which the toothed rotor set is located. Usually, such moveable parts have a sealing surface on the front side, which stretches over its entire surface. The sealing (conforming to the invention) with the help of the rotating crosspiece offers the advantage that the very high frictional forces that arise in the case of the known sealing is reduced considerably, and the toothed rotor sets work more smoothly and thus more efficiently. The rotating crosspiece has a width that represents the optimum condition between the sealing and the friction.
And finally, the invention relates to a process for the manufacture of a toothed rotor set, according to which, the set is manufactured through a shaping procedure, preferably with the help of a powder metallurgy process, plastic die casting process, flow pressing process, pressure casting process, particularly aluminum pressure casting and punching process.
An expensive teeth system of this kind required by the toothed rotor set conforming to the invention can be produced simply and cost effectively with the help of this process. Manufacturing through machining, grinding, shaping, knocking and sawing, all of which are generally known to be used for creating teeth systems, cannot be used in the case of the invention, because the teeth system here is very complicated.
In an advantageous design of the invention, the toothed rotor set is used in a pump, particularly a lubrication oil pump for internal combustion engines, gears, hydraulic aggregates and high pressure cleaning systems.
In another advantageous design of the invention, provision has been made for the use of the toothed rotor set as an engine.